It is impossible to control all the variables when it comes to parenting.

当你做父母时，真的没办法控制住所有的变量。

Well, economics is not a traditional science because it is nearly impossible to control all the different variables.

经济学不是一门传统科学，因为要控制所有不同变量几乎不可能。

Each crawler provides independent, infinitely variable control and counter rotation capability.

每个履带都提供独立、无限可变的控制和反向旋转能力。

See, when we study animals in a lab, it’s hard to control variables to research how an animal responds to different environments or to learn about interactions in groups of animals.

看， 当我们在实验室研究动物时，很难控制变量来研究动物对不同环境的反应或了解动物群体之间的相互作用。